The present disclosure relates to technology for measuring a depth to an object using a time-of-flight (TOF) principle, and more particularly, to a depth sensor for extracting a plurality of frame signals having different phases from light reflected from an object and estimating a depth to the object based on the frame signals, a depth estimation method using the same, and a depth estimation device including the same.
Sensors are elements that detect the state or the position of an object and convert a detection result into an electrical signal. Sensors include light sensors, temperature sensors, pressure sensors, magnetic sensors, and depth sensors.
A depth sensor measures a time that a pulse signal has taken to travel from a source to an object (or a target to be measured) and back using the TOF principle and calculates a depth or a distance between the depth sensor and the object. The signal output from the source in the depth sensor may be a microwave signal, a light wave signal, or an ultrasonic wave signal.
Depth sensors, which calculate a depth to an object using the TOF principle, use a plurality of frame signals having different phases. For instance, a depth sensor using a depth pixel with a 4-tap pixel structure simultaneously applies gate signals having 0-degree, 90-degree, 180-degree and 270-degree phase differences from a signal output from a source to the depth pixel and extracts a plurality of frame signals from an optical signal reflected by an object to calculate a depth to the object. A depth sensor using a depth pixel with a 1-tap or 2-tap pixel structure applies gate signals having 0-degree, 90-degree, 180-degree and 270-degree phase differences from a signal output from a source to the depth pixel with time differences and calculates a depth to an object using a plurality of frame signals measured with time differences.
When any one of the frame signals is omitted, an error occurs in the depth to the object calculated by a depth sensor. The omission of a frame signal is highly likely to happen when a depth sensor using a depth pixel with the 1-tap or 2-tap pixel structure operates at high speed, i.e., at a high frame per second (FPS) rate.